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Cheap wonder metals will make a faster, cleaner world

If only aluminium, titanium and magnesium were cheaper, they would replace steel and help us cut fuel bills and emissions. That day may not be far off

By Hal Hodson

There must be a better way

(Image: Jan Woitas/EPA/Corbis)

TESLA’S electric sports car; the Audi A8; Lockheed’s SR-71 spyplane&colon; only the fastest, sleekest vehicles and aircraft have been made from high-grade aluminium, magnesium and titanium. These wonder metals are light and strong, but have a downside, namely their high cost and the large amounts of energy needed to produce them. Only the rich and powerful have enjoyed their benefits – until now.

The US government is funding a group of projects that aim to unleash light metals for the masses. Run by the Department of Energy’s research arm ARPA-E, the METALS programme aims to make aluminium and magnesium cost the same as steel, while titanium could become as cheap as the slightly pricier stainless steel.

Last week 18 teams presented their work at ARPA-E’s annual energy innovation summit in Washington DC, showing new ways to produce these metals and handle valuable scrap.

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ARPA-E’s primary goal is to reduce the energy that goes into transport – by making cars and planes lighter. The immediate benefit would be to make them a whole lot zippier and more energy-efficient, and there are many other exciting possibilities further down the road (see “Talented Titanium“).

Steel is much used in motor vehicles and load-bearing structures, like bridges. Aluminium, magnesium and titanium would be better in most cases, but are prohibitively expensive.

“Titanium is the best structural metal there is,” says James Klausner, who leads METALS. “It’s lightweight, it’s strong and it lasts forever because it does not corrode.” He sees titanium potentially displacing steel – if the price would only fall from &dollar;35 to &dollar;4 per kilogram.

ARPA-E’s stance is that reducing the energy cost of light metal production would benefit the US in the same way as its recent glut of cheap gas, by bringing it closer to energy independence. “Light metal production consumes a lot of energy,” says Klausner. “If you’re importing metal from overseas, that’s tantamount to importing energy.”Better, he says, “to use our domestic ore to produce domestic metal”.

Massachusetts-based Infinium is one firm aiming to revolutionise aluminium production. It is exploiting a new kind of electrochemical cell that separates the metal from its ore without generating carbon dioxide, a by-product of traditional methods. Chief technology officer Adam Powell says their process is 30 per cent more energy-efficient, and the company is already producing rare earth metals like neodymium and dysprosium in this way.

Magnesium is present in huge quantities in the ocean, but at such low concentrations that extracting it is very energy-intensive. At the Pacific Northwest National Laboratory in Richland, Washington, researchers have partly solved that problem, using a catalyst that reduces the working temperature of the process from 900 to 300 °C.

By bringing the energy cost down and making lightweight metals the stuff of everyday manufacturing, ARPA-E hopes there will be other major benefits too. According to Klausner, “lightweighting” all cars and planes in the US would save 121 billion litres of fuel a year and cut carbon emissions by about 5 per cent.

If all US planes and cars used lightweight metals, it would cut carbon emissions by 5 per cent

But if such projects succeed, we will have to tackle another challenge – recycling these light metals. Iron and steel can easily be pulled out of a waste stream using magnets, but that doesn’t work with aluminium and magnesium. The latest model of Ford’s famous F-150 truck, which sells in the hundreds of thousands each year, contains far more aluminium than any previous model. Getting all that metal back out is uneconomic in the US at present.

So ERCo, a company based in Plainfield, New Jersey, is working to adapt a steel recycling technique for use with aluminium. The firm uses lasers to determine the composition of a vat of molten metals derived mainly from aluminium scrap. An automated system then adds more scrap – chosen to turn the mix into a desired alloy.

Gravelly gold

Scrap which contains aluminium is currently crushed and shipped to China, India or Bangladesh, where it is painstakingly sorted by hand. Known as zorba, this gravelly mixture of shredded car seat fabric, aluminium chunks and copper wiring is a human-made gold mine in countries with low labour costs, but shipping it there in the first place wastes energy (see map).FIG-mg30102301.jpg

A University of Utah spin-out uses a finely tuned varying magnetic field to do the same sorting without human intervention. Different metals feel the field to different degrees, depending on how it interacts with their atoms. The demo unit I saw running on the ARPA-E conference floor perfectly sorted a conveyor belt feed of copper and brass from aluminium, spitting each metal into its designated container. The firm will trial the technology this year at a plant in Plymouth, Utah, owned by Nucore – the largest steel producer in the US – which generates much of its own raw materials via recycling.

Together, these technologies will make for a world that is much lighter on its feet. And just as most of us don’t pay much attention to the steel bridges and beams that surround us, so newly cheap, light metals will start to blend in too. Most of us will get on with business as usual – we’ll just be moving a bit faster.

Talented titanium

When Napoleon III wowed his guests with pricey aluminium cutlery, those present could hardly have foreseen that a fall in the metal’s cost would usher in an age of air travel and spacecraft. The same goes for the impending light metals revolution.

Sleek cars and fuel efficiency are nice, but what else might ubiquitous light metals unlock? Cheap titanium is particularly promising. With it, we could build structures impervious to creeping salt corrosion, not just on land, but in the ocean too. Replacing steel with non-corroding titanium could skirt one of the main obstacles to wave power’s adoption.

Titanium could also be used to make wind turbine blades that are easier to spin up. Air travel would become cheaper as planes like the Airbus A380 or the Boeing Dreamliner become standard, not the luxurious long-haul exception. Robots will even get safer as a titanium skeleton carries less momentum, so a moving robot arm is less able to hurt humans.

This article appeared in print under the headline “Heavy metal is so last year”